Stabilizing means for electric power systems

ABSTRACT

A breaking resistor is connected to an electric power circuit remaining with light load condition during the reclosing period in the faults of said circuit. The breaking resistor comprises a coiled resistive wire wound around an axis inserted in an insulator cylinder, a plurality of insulating spacers in said coiled wire placed in such a manner that each of the adjacent turns of said coiled wire is spaced apart from the adjacent turn so that a duct to flow a cooling medium is defined by surfaces of said adjacent turns of wire and surfaces of adjacent insulating spacers.

[72] Inventors Kazumi Morirnoto;

Appl. No. Filed Patented Assignee Priority Hachiro Miyao; TakeoKuwabara, all of Yokohama-shi, Japan Apr. 24, 1968 Oct. 5, 1971 TokyoShibaura Electric Co., Ltd. Kawasakbshi, Japan Apr. 27, 1967, Apr. 25,1967, June 3, 1967 Japan Z/34,963, 42/254,220 and 42/46,864

STABlLlZlNG MEANS FOR ELECTRIC POWER SYSTEMS 7 Claims, 8 Drawing Figs.

US. Cl

Int. Cl

FieldoiSearch 338/53,55,

[56] References Cited UNITED STATES PATENTS 1,389,105 8/1921 Simmon338/55 2,147,481 2/1939 Beetlestone et al 338/55 2,715,671 8/1955Harrison 338/58 Primary Examiner-Rodney D. Bennett, Jr. AssistantExaminer-T. H. Tubbesing Attorney-Geroge B. Oujevolk ABSTRACT: Abreaking resistor is connected to an electric power circuit remainingwith light load condition during the rcclosing period in the faults ofsaid circuit. The breaking rcsistor comprises a coiled resistive wirewound around an axis inserted in an insulator cylinder, a plurality ofinsulating spacers in said coiled wire placed in such a manner that eachof the adjacent turns of said coiled wire is spaced apart from theadjacent turn so that a duct to flow a cooling medium is defined bysurfaces of said adjacent turns of wire and surfaces of adjacentinsulating spacers.

| CURRENT POTENTIAL Q6 TRANS- FORMER TRANS- FORMER I '1 l IIIIIII I LIIIIIIIII t II III/II IIIIIIIIII DIRECTIONAL DISTANCE ,R LAY TRlPPlNGREC LOSI NG CONTROLLER i POWER E i POWER SOURC CONTROLLER STABILIZINGMEANS FOR ELECTRIC POWER SYSTEMS This invention relates to a means forstabilizing transmission lines, and more particularly to a stabilizerfor an electric power circuit, in which said stabilizer functions as atemporary load which consumes the electric power of power systems whenfaults are removed from the system and during the reclosing operation ofthe system.

In transmission lines or systems, there are troublesom problems, such asshort circuiting over two or three phases, only one line being groundedand the like. In these cases, power circuit breakers near faultpositions will break out fault current and thus the power system will beseparated into at least two systems. This results in the followingproblems as is well known, that is to say, if one of the powertransmission lines separated from the others loses a heavy load, thestep out current frequency in said line or the power system will beincreased to a value higher than the value obtained prior to theseparation from the other system by reason of the absence of the loadthereof, and the mechanical input of generators connected with saidtransmission line will be in excess.

Such a condition causes a subsequent synchronizing operation betweenboth separated power systems to become difficult because of the greatdifferences in frequency or phases between said systems. Then, it isnecessary to expend much time for the synchronizing connection betweensaid two systems, and during this time period, interruption of serviceoccurs.

Accordingly, it is necessary to provide a device to avoid interruptionof service over a lengthy period of time. Usually, such a device iscomposed of a resistor connected to the terminal of said transmissionline, in which said resistor functions as an effective dummy load toprevent its phase shifting relative to another system or anothertransmission line. However, there is another problem in which ahigh-power transmission line is of extra high voltage such as 275 kv. or500 kv. and moreover, some troublesome problems are introduced into thedesign and construction thereof.

One of the problems is to provide a small size resistor which absorbsthe high-tension power energy of the lost load transmission line havingbeen released from the power station or generators. This reason is dueto the fact that said resistor is used only during the reclosing cycle,and is not normally used. Another problem is directed to cooling for thedummy load or a resistor which generates much heat when it is connectedwith said terminal of the transmission line, in spite of the fact thatsaid connecting period is very short, during which both the breaking outand reclosing operations of circuit breakers in said power transmissionlines or systems will take place. This is caused by the fact that thevoltage of the transmission line is very high, such as 275 kv., 500 kv.or more, then said resistor would be subjected to high-flow currentduring this period, particularly, during a duration which awaits asynchronizing connection.

Accordingly, an object of the present invention is to provide animproved stabilizer or resistor of small size and of low cost.

Another object of the present invention is to provide an improvedstabilizer having an excellent cooling efficiency.

A further object of the present invention is to provide a resistor whichis fabricated easily without the necessity of providing a large spacewith other components.

A still further object of the present invention is to provide astabilizer which can promote stabilization on a high-tensiontransmission systems, which may be subjected to heavy disturbance duringreclosing cycles.

Briefly stated, in accordance with the present invention, there isprovided an apparatus to be connected to an electric power circuitremaining with the light load condition during its reclosing cycle,which comprises at least one coil assembly formed with spiral turns madeof resistance material and wound around an axis; each of said turnsbeing of approximately the same height on a plane across said axis, andhaving a space between adjacent turns. A plurality of insulating spacersare placed in said space in such a manner that adjacent spacers arepositioned in a circumferentially spacedapart relation in a windingdirection of said resistance material so that a duct to flow coolingmedium therein is defined by the surfaces of adjacent turns of theresistance material and surfaces of adjacent insulating spacers, andthere are means for connecting said coil assembly by its terminals tosaid light loaded electric power circuit for a time interval achievingsaid reclosing cycle.

Other objects and features of the present invention will become apparentwhen read in conjunction with the accompanying drawings in which:

FIG. 1 is a sectional elevational view of one embodiment in accordancewith this invention;

FIG. 2 is a cross-sectional view taken along a line ll-ll in FIG. 1;

FIG. 3 is an elevational view of another modification, partly brokenaway and in section of the stabilizer according to the invention;

FIG. 4 is a front view, partly broken away, of a portion of a resistorelement shown in FIG. 3; and

FIGS. 5, 6, 7 and 8 are views of resistor elements, partly in sectionand partly broken away, of further embodiments according to theinvention.

Referring now to FIG. 1, there is a stabilizer or resistor generallyshown by the reference numeral 10, having an enclosure 11 which includesa tubular insulator member 12 made of a suitable insulating materialsuch as porcelain glass reinforced epoxy resin and the like, and anoiltight top cover member 13 made of metal and which acts also as ahigh-potential terminal to be connected with one of transmission lines.The top member 13 has a terminal 14 to connect said transmission linethereto, and is tightly attached to an opening 15. The enclosure 11 alsois provided with an opening 25 through a bottom wall 16 thereof, and acylindrical tubular member 17, which extends through the opening 25, isprovided within said enclosure 11, by aligning its longitudinal axiswith the longitudinal axis of said enclosure 11. The tubular member orpipe 17 has an upper opening or outlet 19 for feeding the insulating andcooling oil into said enclosure 11 which includes several spaces ofparts described hereinafter, and an inlet 20 positioned on the bottomwall of it to conduct the oil therein- 10.

There is provided a winding generally shown by the reference numeral 21wound around the tubular member 17. The winding is comprised by a longwire-shaped resistance material 22 wound in helical form, and theresistance wire may also be made as a form in bar. The wire 22 is madeof material such as soft iron, silicon steel and any other suitableresistance materials which are preferable to be selected from the grouphaving relatively a large heat capacity. Such resistance wire or elementis covered with a plurality of insulating layers 23 each of which ispositioned around said resistance wire or bar 22. Further they areprovided on wire 22 in such a manner that each of them is spaced apartfrom each other along the length of said wire element 22. The insulatinglayers 23 are made of materials such as a combination of polyester resinand insulating paper, in which the former is placed inside the latter.

The winding 21 mentioned hereinbefore is composed of a plurality ofcoils 22 disposed around the cylindrical tubular member 17 with adistance along the axis thereof, wherein all of said coils 22 areapproximately similar both in inside and outside diameters,respectively. These coils 22 are connected in series, one end of whichis connected to a high-voltage terminal l4, and the other is connectedto an earthing or neutral terminal 26 provided on the portion under theinsulating tubular member 12. As is clearly shown in FIG. 1, each of thecoils 22 is supported in a vertical direction to each other bysupporting members 28 which serve to make cavity or space 37 whichallows insulating and cooling oil to flow therethrough. The coilassembly or winding 21, also, is fixed by positioning it between both ofan upper clamp plate 29 and a lower clamp plate 30. Since such clampingplate is well known in the art. the explanation thereof is omitted.

The bottom wall 16 of the enclosure 11 is provided with an opening 31.The opening 31 is connected to an oil circulating pump 32 via an oilduct 33, so that the insulating and cooling oil in the enclosure 1 1 isconducted into the opening 31 from the bottom portion thereof, and thenthe pressure risen oil resulted from forced pumping operation by thepump 32 is conducted to a cooling means 34 for said oil through aconduit or duct means 35. Any suitable form may be used as theabove-mentioned oil cooler 34 as is well known in the art. Thus the coilcooled by said cooler or heat exchanger 34 is forced into the opening 20through a conduit or duct 36, and then enters into the interior of thetubular member 17 from the bottom thereof. Thus the flow of theinsulating and cooling oil will be forced to direct upwardly in thetubular member 17.

Referring now to FIG. 2, in which the same parts are shown by the samereference numerals as those shown in FIG. 1, there is shown one of thecoil assemblies 21 in such a manner that said coil assembly 21 isconstructed in spiral or helical form in plane view. In the figure, itwill be easily understood that many spacers or passages 28 acting as thecooling oil path are provided between adjacent insulating layers 23along the lengthwise direction of said resistance element 22 and in aradial direction thereof, which the oil or coolant flows therethrough,and these spaces 37 are also disposed in a radially spaced relation in aplane through the diameter of coil assembly 21, and in a tangentiallyspaced relation to each turn of said coil assembly. Stated further,since the substantial portions of the resistance element 22 arepositioned within said spaces 37 in normal state or exposed one, it willbe understood that the resistance element 22 is effectively cooled byinsulating and cooling oil contacting directly to said resistanceelement 22.

Furthermore, in accordance with the embodiment, in addition to theeffectiveness mentioned above, the stabilizer or resistor for use duringthe reclosing cycle of transmission line can be provided without highexpense by the reason of the fact that an area is provided sufficientlyto remove the generated heat during the operation of resistance element22 in actual, as is clearly shown in FIG. 2. In FIG. 2, also, it isobserved that said exposed surface of resistance element 22 within theenclosure 11 exists in a space 37 between adjacent insulating layers 23,and many of these spaces 37 and exposed surfaces of resistance element22 are provided therein. Thus the cooling effect to the stabilizer coils22 can be increased.

Further stating, said cooling effect to the coil member 22 is moreincreased by forced flowing of oil by pumping with a pump 32 in such amanner that the oil heated by coil assembly 21 is absorbed from theopening 31 of the bottom wall of the enclosure 11 via an oil duct 33,then the pressurized heated oil will be sent into the cooler 34 throughthe duct 35, thus the oil cooled by the cooler or heat exchanger 34 is,in turn, furnished into tubular member 17 through the duct 36 andopening 20, and then the oil flows into the tubular member from thelowermost end to the uppermost opening 19 thereof. Thus the oil flowsinto the level 27, above which a gas pressure compensating chamber 38absorbing both the increase and decrease in volume thereof according tothe variation of the ambient temperature is provided. In accordance withsuch a forced cooling system, it is clear that the size of thestabilizer can be designed extremely small without high expense. As isclearly seen in FIG. 2, the spaces or passages 37 are arranged in zigzagform along the longitudinal axis of the enclosure 11. This results inturbulence flow in spaces 37 between adjacent coils 22 respectively,which contributes to cooling the resistance element 22 quickly, thus itwill be apparent that cooling effect for the coil assembly 21 is so highthat the stabilizer 10 having a small size can be obtained without highexpense.

In order to run the pump 32 during only the time of interval relating tothe reclosing cycle to reduce the idle expense of electric power to themotor of pumping means, there is provided some additional devices asfollows. Generally, in the transmission lines. protection devices areprovided therein. One of such devices is a distance relaying protectingmeans which acts to break the section on the transmission line to beprotected upon occurrence of faults, for example, short circuitingbetween two phases or among three phases of said transmission line.

Referring to FIG. 1 again, there is generally shown the transmissionline to be reclosed after the removal of the faults as reference numeral39, and the right-hand portion thereof is connected to a single powersource and the left-hand one is connected through any suitable circuitbreaker, which acts to remove the faults caused on line 39, to anothersource in which of course said both of opposed sources are held thesynchronization between them during normal operation, in that time thecircuit breaker 40 is closed. It is not necessary to explain thearrangement of the relation between said sources and transmission line39 as it is well known in the art.

As is well known, there is provided a relaying means 41 such as distancerelay, directional distance relay and the like on the terminal of thetransmission line. The terminal has any suitable fault detecting meanssuch as high speed over current relay, high speed under voltage relay,zero phase over voltage relay and the like not shown. The latter willdetect the fault caused on the transmission line 39, and it willcooperate with said distance relaying means 41, causing conventionalcarrier protection devices to function in the usual manner. Brieflystating, the function of them, when a fault such as short circuitingoccurs on the section to be protected, said fault detecting means willdetect it first, approximately at the same time distance relaying system41 functions, which, in turn. causes the carrier means to function todetect if the fault exists in the section to be protected. If said faultexists in said section, these protecting means will function to breakout the circuit breakers of the terminal by cooperating with each other,thus the fault will soon be removed from the transmission line, and thenthe are or ionized atmospheric gas in an arc extinguishing chamber ofthe circuit breaker 40, at the same time, when breaking operationstarts, the reclosing cycle will start. The stabilizer 10 is immediatelyconnected to any point, for example, terminal of line 42 which is nearthe power source not shown. The line or power system 42, in which thestabilizer 10 is connected, is one which has become to a light loadaccording to breaking out the heavy load thereon. Thus the remaininglight load power system 42 will be possible to maintain a relativelystabilized state for the reason of connecting the stabilizer 10 insystem 42. If another remaining power source which is at left hand ofthe transmission line 39 not shown, has a heavier load than said source,it is not necessary to connect the stabilizer because of the fact thatif this is done, said remainder system must have a more increased loadthan the previous one.

In order to achieve this, there is provided a controller 43 havinglinkage means 44 to open and close the circuit breaker 40, and which iscontrolled by the output of protecting relaying systems 41, and theoutput of said reclosing controlling means 43 generates the signal toforce a power controlling means 45. Thus the latter controlling means 45yields to operate the motor in pumping means 32.

It is apparent that the stabilizer 10 is connected in power systemduring only the reclosing cycle, and the pumping means 32 is driven onlyduring the same time interval.

In accordance with the present invention, the coil assembly 21 may beconstructed as shown in FIG. 3, in which the same parts are shown by thesame reference numeral as FIGS. 1 and 2, and their explanation will beomitted. The construction of the coil assembly 21 is similar to that ofthe one shown in FIGS. 1 and 2, excepting an insulating web 223 is woundaround the resistance material 22 with helical form along thelongitudinal direction thereof, as is clearly shown in FIG. 4. Theinsulating material or web 223 may be composed of a plurality ofcontinuous helical rings 224 arranged lengthwise along said resistanceelement 22, in which each of said helical rings 224 is arranged inlengthwise spaced relationship between and against edges of adjacentrings, thus the spaces 37 or oil ducts for cooling the resistanceelement are formed between the adjacent rings, respectively.

In accordance with this embodiment, because of the fact that each of thecoil assemblies 21 is provided with continuous helical insulating webthereon, its winding operation will be achieved with extreme ease sothat the stabilizer according to the present invention can be providedwithout high cost. As the intennediate portions or exposed portions 222positioned between the adjacent rings 224 are directly exposed to oil,the cooling effect will become extremely large. Thus it is easy toprovide a stabilizer of small size, as is evident to those skilled inthe art.

In another embodiment shown in FIG. 5, it is seen that a coil assembly21 comprising a coil member 22 is wound around tubular member 17 whichacts to pass the insulating and cooling fluid therethrough, as mentionedabove. The resistance element 22 is constructed by three layers of webmade of silicon steel material, which is edgewise wound around saidtubular member I7 so that said webs define a helical form on saidtubular member 17. Each of the helical turns 22 is radially separatedfrom each other by spacer members 46 disposed between said adjacentturns, in which said spacer member is constructed in the form of a barof any suitable insulating materials such as glass reinforced polyesterresin or phenol resin and the like, and the insulating bar is of largersize in length than the width or height of web of resistance element 22.Thus, there is no dangerous short circuiting between adjacent coils orresistance elements 22 which are in stacked relation in an axis thereof.

Though the spaces or oil ducts are not shown in FIG. 2, it will beeasily understood that they are provided between the barscircumferentially spaced apart from each other.

In accordance with another embodiment shown in FIG. 6, a portion of acoil 22 of the coil assembly 21 is shown in cross section, wherein saidcoil 22 comprises three webs 47, 48 and 49 made of silicon steel web,which are wound around the cylindrical member or tube as shown in FIG.5. The two strips 47 and 48 are shown as having the same dimensions inheight or width, and arranged in edgewise relation to one another.However, the remaining one strip or web 49 has a width or heightnarrower than said two webs 47 and 48. This reason is as follows.

Generally speaking, when the opposite edges of the strip are cut awayfrom the web material or sheet, there will happen a sharp edge 50alongside of said web material or strip. If the sharp comer of the edgeis against the insulator the front end of said sharp edge 50 will be cutinto the insulating material between adjacent turns of resistanceelement 22, and finally the insulating characteristics of said insulator23 is destroyed. But, in accordance with the constructing mentionedabove, each of the front ends 50 on the sharp edges of said webs isarranged far from the surface of said insulator 23. As is seen in thefigure, the sharp edges 51 of the narrow web 49 or strip are directed tothe adjacent strip 48, and the edges are not directed to the surface ofthe right-hand insulator 23. The insulating material disposed betweenthe adjacent resistance elements 22 will not be destroyed by being cutinto said insulator. Thus the stabilizer will be durable for a longtime.

In FIG. 7, there is shown a further embodiment of the present invention,in which a strip or web-shaped resistance element 52 is provided with aplurality of dimples 53 along the lengthwise direction of said web 52.MOre particularly, these dimples 53 are disposed on the web or strip 52in such a manner that they are positioned on the strip 52 with aspacedapart relation from each other along the lengthwise direction ofsaid strip. Of course, said plurality of dimples 53 may be provided onthe strip 52 in such a manner that, for example, two rows of them are ina direction of longitudinal centerline of the strip 52 may construct azigzag form to said centerline of the strip 52. The strip 52 having sucha construction is wound around the tubular member 17 as is seen in FIGS.1, 2, 3 and 5. In that case, a plurality of the insulating bars 54running parallel with the axis of said tubular member prevent adjacentturns from radially touching, respectively. Thus, the cooling effect ofthe resistance element or strip 52 will become larger than the casewithout such dimples for the reason of that many of said dimples 53having extended heat radiation surface are positioned within oil ductsor spaces 37 and these dimples 53 are directly contacted the coolingmedium or insulating oil flowing through it in a direction vertical tothe drawing, then they will be capable of absorbing much quantity ofheat from said dimples 53 and thus the resistance element 52 is highlycooled.

Said dimples 53 on the strip or resistance element 52 will be easilymade by using a known pressing operation.

It is possible to use resistance material 55 in the form of wire shownin FIG. 8. The resistance element of this embodiment is made of an ironrod or wire 55 having a circular cross section. The element 55 is woundin a coil form after successive operation including pressing successiveportions spaced from each other along lengthwise direction of said rodmaterial 55. This, a plurality of flat portions are formed in a spacedrelation along the lengthwise direction of said rod material 55, ofwhich the opposite heat radiation surfaces are positioned in an oil ductor spaces through which the coolant or insulating oil flows. The flatportions 56 are positioned in an oil duct, flowing coolant throughwhich, in such a manner that the opposite surfaces of each flat portions56 are stood in said duct, in other words, said opposite surfaces offlat portions are arranged approximately parallel with the flow of thecoolant or an axis of tubular member as explained in FIGS. 1, 2, 3 and5, and the effect of them is similar to that of the embodiment shown inFIG. 7. However, with this modification in FIG. 8, it is seen that it ispossible to use a steel rod orwire having standard dimension and whichis commercially available. The stabilizer of transmission lines or powersystems is provided without much labor and high cost. Also the referencenumeral 57 shows the insulators between adjacent turns of resistanceelement 55.

In above embodiments of the present invention, the coil assembliesarranged in the enclosure commonly alternately invert the windingdirection to reduce the inductance through the whole series circuit ofthe coil assembly.

The stabilizer mentioned above is adopted to use atomic power generatinginstallations. In FIG. 1, the terminal or line 42 may be used as theterminal of the generator in said atomic power installation. As is wellknown in the art, an atomic power reactor is generally used under thecondition of generating uniform electric power for the reason of thefact that once the reactor is stopped with any fault resulted frombreaking down the generator out of power system according to the faultsuch as short circuiting on transmission lines or buses to be connectedwith said generator, the restarting of said atomic power reactor willexpend extremely long time interval, since the safety rods or shims willbe entered into active core and vice versa, to stop the reaction of saidreactor. Thus, in the conventional protecting systems, there areprovided means for avoiding such a fault as the reactor stops thereaction thereof. To this end, the protecting systems act to exhaust thefission steam irradiated with the fuel positioned in said vessel into anenclosed condenser, in which said condenser causes all of the fissionsteam generated within said reactor or boiler to condense thereinwithout exhausting to ambient atmosphere. Then the main shutout valve ofthe turbine closes to stop the steam to the turbine wheels, and at thesame time the generator will be broken out of bus forced by thereof,also said stabilizer will be connected to the terminal of saidgenerator. Thus, the dynamic brake functions on generator, and itreduces the speed to a value near a rated synchronous one without goingto over speed which is higher than the rated one.

Thus, it will be clear to those skilled in the art that, after theabove-mentioned protecting operation is finished the stabilizer orbreaking resistor will come to cut out of the terminal of theturbogenerator, and that the set of turbogenerator is continued to runwith approximately rated speed of it.

After this, and after the fault in system has been removed therefrom,said turbogenerator will be connected again to said power system, andthe fission steam which has been exhausted power circuit maintainedunder light load conditions during its reclosing cycle, which comprises:

into said condenser will be again conducted to the turbine in lieu ofsaid condenser.

Thus, the reclosing cycle is terminated, and the While the principles ofthe invention have been described above in connection with specificembodiments, and particular modifications thereof, it is to beunderstood that this description is made only by way of example and notas a limitation on the scope of the invention.

We claim: 1. An apparatus adapted to be connected to an electric a. anenclosed vessel;

b. at least one coil assembly including terminals with a plurality ofcoils each of which is formed with spiral turns made of resistancematerial and wound arounda tubular member, said tubular member and coilassembly being positioned within said vessel;

c. each of said turns being disposed with substantially the same heighton a plane across said tubular member, and having a space between theadjacent turns, a plurality of insulating spacers placed in said spacein such a manner that the adjacent spacers are positioned in a windingdirection of said resistance material so that a duct for flowing coolingmedium therein is defined by the surfaces of said adjacent turns of theresistance material and surfaces of said adjacent insulating spacers;

d. an insulating and cooling medium sealed in said duct and a means forpumping said medium;

e. a heat exchanger;

f. means for serially connecting said vessel, pumping means,

heat exchanger and said tubular member; and,

means for connecting said coil assembly by its terminals to said lightloaded electric power circuit for a time interval attaining saidreclosing cycle.

2. An apparatus according to claim 1, in which said spiral turns aremade of at least one long web or wire formed of resistance material, anda plurality of insulating rings which also act as spacers are positionedaround said resistance material in such a manner that said rings aredisposed around in spacedapart relations longitudinally along saidmaterial.

3. An apparatus according to claim 1, in which said spiral turns ofresistance element are composed of at least one long web or wire formedof resistance material and a long insulating material spirally woundthereon, whereby a space or duct to pass a coolant therethrough isprovided between adjacent spiral turns of the resistance element.

4. An apparatus according to claim 1 wherein said coil as sembly iscomposed of a plurality of webs or strips of resistance materials whichare spirally wound around the same axis in integrally lapped edgewiserelationship, and a plurality of insulating bars or rods arrangedbetween adjacent turns including integrally lapped webs or stripstherein respectively, said bars or rods being disposed between adjacentturns in circumferentially spacedapart relations, and the rod or barmember being in parallel with said axis.

5. An apparatus according to claim 4 wherein said webs or strips arecomposed of at least two sheets lapped edgewise in radial direction tocoil axis, one of them having a longer width or a higher height to saidaxis than another one, both of sheets being lapped with each other todirect sharp edges of opposed sides toward each other, said sharp edgesbeing positioned far from insulating spacers interposed between theadjacent turns, and said another one or narrow one being held in opposedsharp edges of said wider one.

6. An apparatus according to claim 1 wherein said spiral turns made ofresistance material are composed of web or strip, and said web or stripis provided with a plurality of dimples to transmit self-generating heatfor an ambient atmosphere of coolant thereon, said dimples beingdisposed on longitudinally spaced-apart relation of said web or stripand positioned in said duct flowing through said coolant, in which saidweb or strip is disposed in such a manner that the direction of itswidth or height is in parallel with said axis of the coil assembly.

7. An apparatus according to claim 1 wherein said spiral turns made ofresistance material are made of a long wire material having a circularcross section, said wire material being provided with a plurality offlat portions whose surfaces are positioned in said duct in such amanner that said flat portions are arranged in parallel with said axisof coil assembly and said portions are longitudinally spaced apart alongsaid wire material.

1. An apparatus adapted to be connected to an electric power circuitmaintained under light load conditions during its reclosing cycle, whichcomprises: a. an enclosed vessel; b. at least one coiL assemblyincluding terminals with a plurality of coils each of which is formedwith spiral turns made of resistance material and wound around a tubularmember, said tubular member and coil assembly being positioned withinsaid vessel; c. each of said turns being disposed with substantially thesame height on a plane across said tubular member, and having a spacebetween the adjacent turns, a plurality of insulating spacers placed insaid space in such a manner that the adjacent spacers are positioned ina winding direction of said resistance material so that a duct forflowing cooling medium therein is defined by the surfaces of saidadjacent turns of the resistance material and surfaces of said adjacentinsulating spacers; d. an insulating and cooling medium sealed in saidduct and a means for pumping said medium; e. a heat exchanger; f. meansfor serially connecting said vessel, pumping means, heat exchanger andsaid tubular member; and, g. means for connecting said coil assembly byits terminals to said light loaded electric power circuit for a timeinterval attaining said reclosing cycle.
 2. An apparatus according toclaim 1, in which said spiral turns are made of at least one long web orwire formed of resistance material, and a plurality of insulating ringswhich also act as spacers are positioned around said resistance materialin such a manner that said rings are disposed around in spaced-apartrelations longitudinally along said material.
 3. An apparatus accordingto claim 1, in which said spiral turns of resistance element arecomposed of at least one long web or wire formed of resistance materialand a long insulating material spirally wound thereon, whereby a spaceor duct to pass a coolant therethrough is provided between adjacentspiral turns of the resistance element.
 4. An apparatus according toclaim 1 wherein said coil assembly is composed of a plurality of webs orstrips of resistance materials which are spirally wound around the sameaxis in integrally lapped edgewise relationship, and a plurality ofinsulating bars or rods arranged between adjacent turns includingintegrally lapped webs or strips therein respectively, said bars or rodsbeing disposed between adjacent turns in circumferentially spaced-apartrelations, and the rod or bar member being in parallel with said axis.5. An apparatus according to claim 4 wherein said webs or strips arecomposed of at least two sheets lapped edgewise in radial direction tocoil axis, one of them having a longer width or a higher height to saidaxis than another one, both of sheets being lapped with each other todirect sharp edges of opposed sides toward each other, said sharp edgesbeing positioned far from insulating spacers interposed between theadjacent turns, and said another one or narrow one being held in opposedsharp edges of said wider one.
 6. An apparatus according to claim 1wherein said spiral turns made of resistance material are composed ofweb or strip, and said web or strip is provided with a plurality ofdimples to transmit self-generating heat for an ambient atmosphere ofcoolant thereon, said dimples being disposed on longitudinallyspaced-apart relation of said web or strip and positioned in said ductflowing through said coolant, in which said web or strip is disposed insuch a manner that the direction of its width or height is in parallelwith said axis of the coil assembly.
 7. An apparatus according to claim1 wherein said spiral turns made of resistance material are made of along wire material having a circular cross section, said wire materialbeing provided with a plurality of flat portions whose surfaces arepositioned in said duct in such a manner that said flat portions arearranged in parallel with said axis of coil assembly and said portionsare longitudinally spaced apart along said wire material.